MARS -- NASA's Curiosity rover has spotted something curious, a bright and almost metallic object glinting in the soil of the Red Planet, says the space agency.

The $2.5 billion Mars Curiosity rover took its first scoop of Martian soil on Sunday. Pictures showing the first scoop taken from a patch of sand nicknamed "Rocknest" also reveal that "a bright object is visible on the ground" between the scoop and the rest of the rover, says a NASA statement. The tiny glints are less than a tenth of an inch across.

The team has halted scooping tests with the rover to take more pictures of the glinting object. "The object might be a piece of rover hardware," says the space agency statement. The rover will take more close-up images of the bright object today.

"It's fool's gold," jokes neuroscientist Stephen Macknik of the Barrow Neurological Institute in Phoenix, an expert on optical illusions. Mission engineers plan to look at the shiny object from multiple angles. That could help show whether the glint is an optical illusion cased by darker sand surrounding a light patch of soil or if it's a defect in the camera, Macknik says. "Most likely it is a mineral with a lighter color peeping up but they need to check the brightness to be certain," he says.

Mars has a history of curious optical illusions, such as the "canals" imagined by some astronomers a century ago and the "Face on Mars" that turned out to be a shadowy hill once it was viewed by improved cameras a decade ago. Nevertheless, the tiny bright object spotted by Curiosity has attracted plenty of attention from Mars watchers.

"Beats me what it is! It looks real - that is, something is really there - and it doesn't look like a rock," says astronomer Phil Plait of Discover Magazine's Bad Astronomy website. While the glint could be a piece of plastic from the rover, it doesn't look like a screw or important part, says Plait, by e-mail. "I think JPL and NASA are right to stop activities until they can determine if this is just a bit of Martian landscape or something that might have come off Curiosity itself. Either way, it's worth investigating."